####018016586#### FGUS73 KGRR 152140 ESFGRR MIC005-015-025-035-037-045-057-065-067-073-075-077-081-085- 105-107-117-121-123-127-133-139-159-281600- PROBABILISTIC HYDROLOGIC OUTLOOK NATIONAL WEATHER SERVICE Grand Rapids MI 1130 AM EST Thu Feb 15 2024 ...2024 SPRING FLOOD AND WATER RESOURCES OUTLOOK NUMBER 1... This Spring Flood and Water Resources Outlook is for the rivers in Southwest Lower Michigan. ...Flood Outlook Highlights... The overall flood risk this spring is below average across most of Southwest Michigan (Grand and Kalamazoo River basins) and much below average across West-Central Lower Michigan (Muskegon River basin). This reduced risk is mainly the result of significantly less snowpack than normal for this time of year as well as the fact that there is no ice remaining on any of our rivers. ...Flood Terminology... The term minor flooding is used to indicate minimal or no property damage. However, some public inconvenience is possible. The term moderate flooding is used to indicate some inundation of structures and roads near streams. Some evacuations of people and/or transfer of property to higher elevations may be needed. The term major flooding is used to indicate extensive inundation of structures and roads. Significant evacuations of people and/or transfer of property to higher elevations will be needed. ...Probabilistic Outlook... The flood risk this spring is below normal in all river basins in Southwest and West-Central Lower Michigan. The chance of flooding is less than 50% at all of the forecast locations on our rivers. The lone exception to this is along the Maple River at Maple Rapids, where there is an approximate 70% chance of reaching minor flood level (which is still less than the historical average for this location). ...Past Precipitation... The fall and early winter period was much drier than normal. A few weeks during the middle of January brought wetter than normal conditions, but it's been fairly dry since then. ...River Conditions... Water levels on the rivers were near-normal for most of the fall and early winter, before climbing to well above-average by late January as heavy rain and complete snowmelt runoff found its way into the river systems. Water levels remain slightly elevated for this time of year, but it's entirely possible that we've seen our spring "high water" episode already. ...Soil Moisture and Frost Depths... Soil moisture is near-normal right now, only because of the rain and snowmelt episode Lower Michigan experienced in late January. The record-warm winter conditions so far also mean that there is virtually no frozen ground to speak of - even up north near the headwaters of the Muskegon River. ...Snow Cover and Liquid Water Content... The snow cover - including the amount of water being held in that snow - is near historic lows for mid February. Prior to a region-wide light snow event this morning, there was essentially zero snowpack anywhere in the Lower Peninsula. Liquid water content is less than 0.5 inches at all locations. ...River Ice Conditions... The rivers in the Grand and Muskegon River basins briefly formed a stable ice cover during the cold snap in mid January, but by the end of January all of this river ice had melted and broken up. There is currently no significant river ice to speak of anywhere in the area. ...Weather Outlook. The single biggest factor affecting flood risks are the weather conditions during the sensitive period of melting snow. A slow snow melt with little or no rainfall is ideal to avoid flooding. On the other hand, a rapid warmup accompanied by heavy rain is a much worse scenario for spring flooding - especially if the rivers are covered with ice. At this time, the long range weather forecast calls for a continuation of warmer-than-normal temperatures and near-normal precipitation through the end of March. With no significant ice in any of the rivers, and virtually all of the snowpack already melted, our future flood risks will be linked even more than usual to heavy rain events. Currently, there are no heavy rain storms on the horizon over the next week or two, but as we head into March this will remain a concern. In Table 1 below...the current (CS) and historical (HS) or normal probabilities of exceeding minor...moderate...and major flood stages are listed for the valid time period. CS values indicate the probability of reaching a flood category based on current conditions. HS values indicate the probability of reaching a flood category based on historical or normal conditions. When the value of CS is more than HS...the probability of exceeding that level is higher than normal. When the value of CS is less than HS...the probability of exceeding that level is lower than normal. ...Table 1--Probabilities for minor...moderate and major flooding... Valid Period: 02/19/2024 - 05/19/2024 : Current and Historical : Chances of Exceeding : Flood Categories : as a Percentage (%) Categorical : Flood Stages (FT) : Minor Moderate Major Location Minor Mod Major : CS HS CS HS CS HS -------- ----- ----- ----- : --- --- --- --- --- --- :Grand River Jackson 14.0 15.0 16.0 : 28 30 13 15 6 7 :Buck Creek Grandville 9.0 10.5 12.0 : 11 13 7 5 <5 <5 :Grand River Eaton Rapids 6.0 8.0 9.0 : 6 5 <5 <5 <5 <5 Dimondale 13.0 14.0 16.0 : <5 <5 <5 <5 <5 <5 :Red Cedar River Williamston 9.0 10.0 10.5 : <5 <5 <5 <5 <5 <5 East Lansing 7.0 10.0 13.0 : 21 23 <5 <5 <5 <5 :Sycamore Creek Holt 8.0 9.0 10.0 : 36 32 7 7 <5 <5 :Grand River Lansing 11.0 13.0 15.0 : 16 15 <5 <5 <5 <5 Grand Ledge 11.0 13.0 15.0 : <5 <5 <5 <5 <5 <5 Portland 12.0 14.0 16.0 : <5 <5 <5 <5 <5 <5 :Looking Glass River Eagle 7.0 9.0 11.0 : 42 41 8 9 <5 <5 :Maple River Maple Rapids 9.0 11.0 13.0 : 68 71 <5 <5 <5 <5 :Grand River Ionia 21.0 23.0 25.0 : 20 23 <5 <5 <5 <5 :Flat River Smyrna 8.5 9.5 10.5 : <5 5 <5 <5 <5 <5 :Grand River Lowell 15.0 18.0 20.0 : 20 20 <5 <5 <5 <5 :Thornapple River Hastings 7.0 9.0 10.0 : 32 38 <5 6 <5 <5 Caledonia 10.0 12.0 14.0 : 11 17 <5 <5 <5 <5 :Grand River Ada 20.0 22.0 25.0 : 6 11 <5 <5 <5 <5 :Rogue River Rockford 8.0 10.0 11.0 : 14 19 <5 <5 <5 <5 :Grand River Grand Rapids 18.0 21.0 23.0 : 11 15 <5 <5 <5 <5 :Pere Marquette River Scottville 5.5 6.5 7.0 : <5 5 <5 <5 <5 <5 :White River Whitehall 6.0 7.0 8.0 : 6 11 <5 <5 <5 <5 :Muskegon River Evart 12.0 13.0 14.0 : <5 25 <5 9 <5 <5 :Little Muskegon River Morley 6.0 7.0 8.0 : <5 <5 <5 <5 <5 <5 :Muskegon River Croton 9.0 11.0 12.0 : 14 42 <5 5 <5 <5 Newaygo 11.0 14.0 15.0 : 28 54 <5 10 <5 6 Bridgeton 13.0 16.0 17.0 : 31 54 <5 10 <5 6 :Kalamazoo River Marshall 8.0 9.0 10.0 : 6 11 <5 10 <5 8 :Battle Creek Battle Creek 4.0 5.0 6.0 : <5 <5 <5 <5 <5 <5 :Kalamazoo River Battle Creek 9.0 10.0 11.0 : <5 <5 <5 <5 <5 <5 Comstock 9.0 10.0 11.0 : 7 8 <5 5 <5 <5 New Richmond 17.0 19.0 21.0 : 6 10 <5 <5 <5 <5 :St. Joseph River Burlington 6.5 9.0 11.0 : 11 15 <5 <5 <5 <5 :Portage River Vicksburg 5.5 7.0 8.0 : <5 10 <5 <5 <5 <5 :Chippewa River Mt. Pleasant 8.0 11.0 13.0 : 7 21 <5 <5 <5 <5 :Pine River Alma 8.0 10.0 12.0 : 11 16 <5 <5 <5 <5 Legend CS = Conditional Simulation (Current Outlook) HS = Historical Simulation FT = Feet In Table 2 below...the 95 through 5 percent columns indicate the probability of exceeding the listed stage levels (FT) for the valid time period. ...Table 2--Exceedance Probabilities... Chance of Exceeding Stages at Specific Locations Valid Period: 02/19/2024 - 05/19/2024 Location 95% 90% 75% 50% 25% 10% 5% -------- ------ ------ ------ ------ ------ ------ ------ :Grand River Jackson 11.8 12.1 12.7 13.3 14.4 15.2 16.3 :Buck Creek Grandville 6.7 7.0 7.2 7.7 8.4 9.4 11.8 :Grand River Eaton Rapids 4.1 4.2 4.4 4.6 5.3 5.7 6.2 Dimondale 6.7 7.0 7.7 8.3 9.5 10.4 12.0 :Red Cedar River Williamston 4.5 5.5 6.4 6.9 7.6 8.4 8.6 East Lansing 4.5 4.8 5.7 6.1 6.7 7.9 8.3 :Sycamore Creek Holt 6.1 6.4 6.9 7.5 8.3 8.8 9.2 :Grand River Lansing 5.3 6.3 7.3 8.3 9.7 11.6 12.9 Grand Ledge 6.0 6.5 7.0 7.6 8.4 9.4 9.9 Portland 7.1 7.8 8.5 9.4 10.0 11.0 11.5 :Looking Glass River Eagle 4.7 5.4 6.2 6.7 7.7 8.8 9.3 :Maple River Maple Rapids 7.5 8.2 8.8 9.2 9.6 10.2 10.4 :Grand River Ionia 13.4 14.9 17.7 18.8 20.3 21.9 22.4 :Flat River Smyrna 5.0 5.2 5.5 5.9 6.7 7.7 8.3 :Grand River Lowell 8.2 9.5 10.7 11.8 14.0 15.8 16.2 :Thornapple River Hastings 4.5 4.9 5.5 6.1 7.2 7.9 8.4 Caledonia 5.0 5.8 6.5 7.5 9.2 10.2 10.4 :Grand River Ada 11.6 12.8 14.9 16.2 18.2 19.8 20.1 :Rogue River Rockford 5.2 5.6 6.1 6.6 7.3 8.3 8.7 :Grand River Grand Rapids 8.3 9.8 11.9 13.6 16.6 18.1 18.4 :Pere Marquette River Scottville 2.4 2.8 3.3 3.8 4.3 4.6 4.8 :White River Whitehall 3.1 3.6 3.9 4.3 5.2 5.8 6.1 :Muskegon River Evart 8.3 8.5 9.1 9.7 10.6 11.2 11.9 :Little Muskegon River Morley 2.9 3.1 3.4 4.0 4.6 5.0 5.4 :Muskegon River Croton 6.3 6.7 7.2 7.8 8.5 9.4 10.1 Newaygo 8.6 9.1 9.6 10.2 11.1 12.4 13.6 Bridgeton 9.7 10.4 11.0 12.0 13.2 14.8 15.8 :Kalamazoo River Marshall 5.0 5.1 5.4 6.0 6.6 7.2 8.2 :Battle Creek Battle Creek 1.4 1.5 1.8 2.1 2.3 2.8 3.1 :Kalamazoo River Battle Creek 3.8 3.9 4.3 4.8 5.5 6.4 6.9 Comstock 4.9 5.1 5.6 6.4 7.3 8.6 9.5 New Richmond 13.4 13.7 14.1 14.7 15.5 16.3 17.0 :St. Joseph River Burlington 5.0 5.2 5.5 5.7 6.1 6.6 7.0 :Portage River Vicksburg 4.4 4.5 4.7 4.9 5.2 5.4 5.5 :Chippewa River Mt. Pleasant 4.4 4.8 5.1 5.7 6.9 7.7 8.6 :Pine River Alma 4.3 4.9 5.2 6.0 7.2 8.2 8.4 In Table 3 below...the 95 through 5 percent columns indicate the probability of falling below the listed stage levels (FT) for the valid time period. ...Table 3--Nonexceedance Probabilities... Chance of Falling Below Stages at Specific Locations Valid Period: 02/19/2024 - 05/19/2024 Location 95% 90% 75% 50% 25% 10% 5% -------- ------ ------ ------ ------ ------ ------ ------ :Grand River Jackson 10.5 10.3 10.2 9.9 9.7 9.5 9.4 :Buck Creek Grandville 4.9 4.9 4.8 4.7 4.7 4.6 4.6 :Grand River Eaton Rapids 4.0 3.9 3.9 3.8 3.7 3.7 3.7 Dimondale 6.3 6.3 6.0 5.6 5.4 5.2 5.0 :Red Cedar River Williamston 3.1 3.1 2.9 2.7 2.6 2.5 2.4 East Lansing 3.9 3.8 3.7 3.5 3.5 3.4 3.3 :Sycamore Creek Holt 3.3 3.3 3.2 3.1 3.1 3.1 3.0 :Grand River Lansing 4.8 4.6 4.3 3.8 3.6 3.3 3.0 Grand Ledge 5.8 5.8 5.6 5.5 5.4 5.2 5.1 Portland 6.7 6.6 6.3 6.0 5.9 5.7 5.5 :Looking Glass River Eagle 4.0 3.9 3.8 3.5 3.3 3.2 3.1 :Maple River Maple Rapids 5.9 5.5 5.2 4.6 4.3 4.1 4.0 :Grand River Ionia 12.0 11.7 11.2 10.7 10.2 9.9 9.7 :Flat River Smyrna 4.2 4.2 4.1 3.9 3.8 3.7 3.5 :Grand River Lowell 7.2 7.0 6.8 6.5 6.2 5.9 5.7 :Thornapple River Hastings 3.7 3.6 3.5 3.4 3.3 3.1 3.1 Caledonia 4.2 4.2 4.0 3.8 3.6 3.5 3.4 :Grand River Ada 9.7 9.4 9.1 8.4 7.9 7.3 6.9 :Rogue River Rockford 4.6 4.6 4.5 4.3 4.2 4.0 3.9 :Grand River Grand Rapids 5.5 5.0 4.7 4.0 3.4 2.8 2.4 :Pere Marquette River Scottville 1.6 1.6 1.5 1.4 1.2 1.1 1.0 :White River Whitehall 2.0 2.0 1.9 1.8 1.7 1.6 1.5 :Muskegon River Evart 7.4 7.4 7.3 7.3 7.2 7.0 6.9 :Little Muskegon River Morley 2.4 2.4 2.3 2.3 2.3 2.3 2.2 :Muskegon River Croton 5.3 5.3 5.2 5.1 5.0 4.8 4.7 Newaygo 7.8 7.7 7.7 7.6 7.5 7.3 7.2 Bridgeton 8.4 8.3 8.2 8.1 7.9 7.6 7.5 :Kalamazoo River Marshall 4.2 3.9 3.2 3.2 3.2 3.2 3.2 :Battle Creek Battle Creek 1.1 1.1 1.1 1.0 1.0 0.9 0.9 :Kalamazoo River Battle Creek 3.6 3.5 3.4 3.3 3.1 3.0 3.0 Comstock 4.8 4.7 4.5 4.4 4.2 4.1 4.1 New Richmond 12.6 12.4 12.0 11.5 10.8 10.5 10.5 :St. Joseph River Burlington 4.5 4.3 4.2 4.1 4.0 3.9 3.8 :Portage River Vicksburg 4.1 4.1 4.0 4.0 3.9 3.8 3.7 :Chippewa River Mt. Pleasant 3.6 3.5 3.5 3.4 3.4 3.3 3.3 :Pine River Alma 2.6 2.4 2.2 2.0 1.8 1.7 1.5 These long-range probabilistic outlooks contain forecast values that are calculated using multiple season scenarios from 30 or more years of climatological data...including current conditions of the river...soil moisture...snow cover...and 30 to 90 day long-range outlooks of temperature and precipitation. By providing a range of probabilities...the level of risk associated with long-range planning decisions can be determined. These probabilistic forecasts are part of the National Weather Service's advanced hydrologic prediction service. Visit our web site weather.gov/grr for more weather and water information. The next outlook will be issued on February 19th. $$ AMD